1. Field of the Invention
The present invention relates to a flat panel display, and more particularly, to a flat panel display that transmits gray scale value as data, to a column driver circuit, which then digitize them into gamma data, so that column signals can be selected by matching thus-converted analog signal to R, G, B data.
2. Description of the Related Art
Recently, there has been a significant development in flat panel display devices adopting liquid crystal display device or plasma display panel technology. And flat panel displays such as liquid crystal displays or plasma displays adopted for applications, such as computer monitors and televisions, are marketed and commonly available.
Specifically, liquid crystal displays for displaying images utilizing electrical and optical characteristics of liquid crystal become to have screens large in size with high resolution. Liquid crystal displays are configured in that a liquid crystal display panel, i. e., a flat panel for displaying images, a control board and an optical module are assembled to a display module which then is mounted into a case.
Typically, circuits mounted to such display module consist of a controller, power unit, gate voltage generating unit, gradation voltage generating unit, column driver ICs and scan driver ICs. As display devices have large size screens, solutions for EMI trouble, noise problem caused by transmitting media, and high resolution related to restriction in data transmission become absolute necessities.
In order to overcome EMI trouble, while at the same time accomplishing high speed data transmission with low power consumption, a method of transmitting, in a differential signal, video signals including data is proposed. In detail, data transmission technique adopting differential signaling method such as LVDS (low voltage differential signaling), RSDS (reduced swing differential signaling), or TMDS (time minimized differential signaling) system is disclosed, and a study on such technique is in progress.
However, such techniques still suffer drawbacks in that a lot of wires are connected between a control board and a column driver in a display module. These wires transmit R, G, B data, gradation voltage, column control signal and scan control signal. When R, G, B data are represented in 6-bits per color, 18-bits color data are transmitted. To this end, when data transmission is carried out in TTL (transistor-transistor logic) system, 18 wires are required to arranged at a column driver IC, and wires for transmitting column or scan control signals are added. When color data are represented in 6-bits in order to express column signals in each gradation, gradation voltage for expressing 64 gradations has to be supplied to the column driver IC. Further, when bipolarity is taken into consideration, wires for supplying gradation voltage for 128 gradation are needed between the gradation voltage generating unit and the column driver IC.
Such a wire requirement for data transmission can be decreased significantly if data transmission method is changed from TTL system into the above-mentioned differential signaling system. However, there still exists a need for a method of decreasing wires for gradation voltage and minimizing mounting area of control board. As one of the solutions for these matters, multi-layer PCBs are employed. However, it is not cost effective.
As for gradation voltage, it is difficult to obtain a correct gradation value when an image is formed at a screen since the gradation voltage is influenced by the wire resistance while the gradation voltage is applied from the gradation voltage generating unit to each of column driver ICs. Further, complementary circuits for compensating such drawbacks are additionally required.